Theoretical approach of three-dimensional (3D) plasma dipole oscillation (PDO) for terahertz-driven electron linear acceleration

J. Lee, H. S. Song, D. Park, M. Kumar and M. S. Hur

 Laser-plasma-based terahertz (THz) sources usually emit broad-band THz waves, e.g., CTR or two-color scheme. In contrast, from our novel THz source, where we generate plasma dipole oscillation (PDO) as an emitting antenna, we can generate electromagnetic radiation with narrow bandwidth at the plasma frequency in the THz spectral range , where  is the local plasma density) [1]. The PDO can be created by colliding two, detuned laser pulses in a plasma. Bunches of electrons are trapped in the moving train of beat potential of the two laser pulses and are displaced to accumulate the electrostatic force. These trapped electron bunches then commence harmonics oscillation. Recently, various methods for increasing the conversion efficiency of THz radiation sources have been studied. According to our previous study [1], we found that PDO's conversion efficiency theoretically reaches ~10% when the pulse shape, duration, and detuned frequency are optimized such that the maximum electrostatic force can be built-up from minimal driving ponderomotive force. In this presentation, we present our recent study on increasing the efficiency of PDO generation by adjusting the pulse shape; we can decrease the driving pulse energy that is necessary to obtain a given amount of PDO energy, leading to an increased efficiency of THz emission from PDO. According to recently results, we found that driving pulse energy can be reduced by changing the pulse shape, resulting in and obtained twice as high efficiency (0.41x10^-3 -> 0.84x10^-3).

[1] Kwon, Kyu Been, et al. "High-energy, short-duration bursts of coherent terahertz radiation from an embedded plasma dipole." Scientific reports 8.1 (2018).

[2] Lee, Jaeho, et al. "Intense narrowband terahertz pulses produced by obliquely colliding laser pulses in helium gas." Physics of Plasmas 30.4 (2023).